Chloroquine-induced erythema multiforme-like rash in a rheumatoid arthritis patient: A clinicalpresentation and management

Background

Chloroquine (CQ), a synthetic 4-aminoquinoline, has been widely used since its introduction in 1947 for the prevention and treatment of Plasmodium falciparum malaria. Its mechanism of action involves disrupting the parasite's ability to detoxify heme. Beyond its antimalarial role, chloroquine is frequently prescribed for autoimmune disorders such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) due to its immunomodulatory effects. Despite its inclusion in the WHO's List of Essential Medicines for its affordability and efficacy, chloroquine is associated with adverse effects, including gastrointestinal disturbances, headaches, skin rashes, cardiotoxicity, retinal damage, and hepatotoxicity. Long-term use may also result in neuromuscular, neuropsychiatric, and renal complications, requiring careful monitoring, particularly in vulnerable populations.

Case

A 48-year-old male, diagnosed with rheumatoid arthritis based on clinical and laboratory findings, was started on chloroquine 250 mg daily, folic acid 5 mg weekly, and paracetamol for symptom relief. After 15 days of therapy, the patient developed a progressive erythematous rash with maculopapular and targetoid lesions primarily affecting the hands, forearms, and trunk. A skin biopsy revealed histopathological features indicative of a drug-induced hypersensitivity reaction, including spongiosis, epidermal necrosis, and perivascular lymphocytic infiltration with eosinophils. Following the confirmation of a chloroquine-induced hypersensitivity reaction, the drug was discontinued, and the patient was treated with prednisolone 20 mg daily and omeprazole 20 mg twice daily. The rash resolved within days of initiating treatment.

Conclusion

This case highlights a rare but significant dermatological adverse effect of chloroquine, manifesting as an erythema multiforme-like hypersensitivity reaction. Early recognition and prompt discontinuation of the offending agent, coupled with appropriate symptomatic management, are critical to patient recovery. Clinicians must remain vigilant for such adverse reactions, particularly in patients prescribed chloroquine for autoimmune conditions like RA.